Systematic Team Approach to Drilling Optimization Reduces Well Construction Time by 15%, Ghadames Basin, Algeria

Abstract

Drilling through highly inter-bedded Tertiary to Devonian age formations in the Menzel Lejmat Field, Algeria presents a number of distinctive challenges. Problematic overburden consists of abrasive sands, inter-bedded evaporite/carbonate sections, inter-bedded sand/claystone formations in addition to a 30-meter band of extremely hard dolomite. Rock strengths vary greatly with sonic transit times ranging between 55 to 140 milliseconds. Recently, Burlington Resources identified a need to improve drilling efficiency through these problematic formations. They contracted a drilling optimization service (Baker Hughes OASIS) to perform a detailed performance study of offset wells in order to plan and implement a more efficient drilling program for well (MLC-2). The objective was to increase penetration rates, preserve borehole stability, reduce the number of bits and lower overall drilling costs. After analyzing offset wells to benchmark current performance, the service team developed an optimization plan that outlined key areas for improvement. This study included depth based drilling data, wireline log data and daily drilling reports from offset wells. This information was analyzed and a report generated that included projected lithology and mechanical rock properties as well as potential drillability problems. The team recommended specific bits, BHAs and operating practices to address these problems. A summary report of each hole section was provided for use at the rig site to ensure planned goals and targets were achieved. The report outlined depths at which potential problems could occur and what operating practices should be followed to eliminate or to minimize their severity. The drilling of MLC-2 was a significant success. The 12–1/4" hole section was drilled with one bit for the first time and hole quality was greatly improved. The well was drilled six days ahead of the AFE curve and five days ahead of the best performing offset. This represents a 15% reduction in well time saving approximately $300,000. A detailed post-well analysis was performed to document performance achieved and to carry the numerous lessons learned forward. Additionally, subsequent wells were analyzed in a similar manner with special attention given to the 12–1/4" and 6" hole sections. Performance improvement on these wells demonstrated that a continuous improvement process allied with a Polycrystalline Diamond Compact (PDC) development initiative, ensured bit design was optimized for rate of penetration (ROP) and length of run. The authors will document penetration rate and run length records achieved using this process. This paper will also describe process improvements and how lessons learned were fed back into the continuous improvement process to build momentum. Introduction Burlington Resources operates the Menzel Lejmat Block 405 in the Berkine Basin, Algeria. The block is located 130 miles southeast of Hassi Messaoud, northern Algeria (Figure 1). Burlington Resources have drilled 29 wells, including eight exploratory "wildcats." Five separate filed discoveries have been made on the block. During 2000 Burlington Resources moved into the first stage of development drilling in the MLN field. In 1999, the operator identified that undertaking a systematic drilling performance improvement initiative could yield significant efficiency and cost saving benefits. The drilling challenge was to increase penetration rates, preserve borehole stability, reduce the number of bits used per hole section and reduce overall drilling costs. Block 405 can be divided into 3 areas (Figure 2) MLSE in the Southeast part of the block, MLN in the central part and MLNE in the Northeast corner. Wells drilled to date are shown in Figure 3.

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Lessons Learned from Integrated Analysis of GOM Drilling Performance

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